1. Field of the Invention
This invention relates to knock detection and pressuring sensing for vehicle engines.
2. Prior Art
Spark knock in a vehicle mounted internal combustion engine produces a vibration or characteristic pinging sound. Typical causes of knock include incorrect ignition timing of the combustible mixture in the cylinder and too fast burning of the combustible mixture.
Various knock sensors for detecting knock are known. Typically, upon detection of knock, the spark is retarded to eliminate knock. Known knock detectors include various accelerometers wherein a mass vibrates in response to engine vibration. This vibration is sensed electrically to produce an output signal. For example, a piezoelectric crystal mounted on a disc free to vibrate can produce an output electric signal.
Furthermore, various pressure sensors are also known. For example, a sealed reference pressure volume adjacent a movable diaphragm can detect pressure changes. Pressure signals indicating barometric or manifold absolute pressure can be used to control engine operation.
To obtain information indicative of the pressure and the occurrence of knock it is known to use two sensors. Each of these sensors requires separate fabrication and separate installation. It would be desirable to obtain knock and pressure information and concurrently reduce cost, simplify the control apparatus and reduce weight. These are some of the goals this invention achieves.